Trying to generate a string that becomes a variable name in Freemarker or a "derived variable name" - freemarker

Question

I'm using a data-directive or list to pull in several values, of which, I don't know how many there will be, and I want to try and list through them, and create several variables in the list if you will.
<#list 1..10 as x>
<#-- the next line doesn't work, but what i'm trying to fix -->
<#assign .vars['VAR'+x?string] = rand(100) />
</#list>
But I can list them back out that way.
<#list 1..10 as x>
${.vars['VAR'+x?string]}
</#list>
The documentation for assign, says:
name: name of the variable. It is not expression. However, it can be
written as a string literal, which is useful if the variable name
contains reserved characters, for example <#assign "foo-bar" = 1>.
Note that this string literal does not expand interpolations (as
"${foo}").
Is there no way around this? Am I trying to do the impossible? Is there some way I can insert a derived name into the .vars... Hash is it?
A little more research that was close, but didn't get me there:
This prevoius question gives how to READ the derived variable, but I need to WRITE/CREATE the derived variable.
FreeMarker get variable value by concatenating another variable value
This prevoius question shows that I can use a string to assign a variable and re-iterates what we saw in the first link.
Variable name in Freemarker Template Language

Answer 1

As FreeMarker can't assign to elements of collections (but you can ?map(it -> ...) a collection to another), the only way is via ?interpret:
<#list 1..10 as x>
<#-- the next line doesn't work, but what i'm trying to fix -->
<#'<#assign VAR${x?c} = rand(100)>'?interpret />
</#list>
I wonder why do you need to assign to a dynamically named variables though, since reading dynamically named variables is also a pain, even if a lesser one.

Answer 2

Ultimately, I believe the correct way to phrase my solution was a sequence of hashes:
<#list 1..z_Coupon_Pet.NUM_COUPONS as x>
<#assign INSTORE_COUPON=call_coupon_from_table1() />
<#assign ONLINE_COUPON=call_coupon_from_table2() />
<#assign coupon_string_row= '{
"COUPON_NUM" : ${x},
"INSTORE" : "${INSTORE_COUPON?js_string}",
"ONLINE" : "${ONLINE_COUPON?js_string}"
}' />
<#if x==1>
<#assign coupon_hash_string = coupon_string_row />
<#else>
<#assign coupon_hash_string = coupon_hash_string + ',' + coupon_string_row />
</#if>
</#list>
</#if>
<#if coupon_hash_string?has_content>
<#assign coupon_hash=parsejson('[' + coupon_hash_string + ']') />
</#if>
We specifically avoid <#assign my_hash = my_hash + element /> because of this note in the documentation:
Note that hash concatenation is not to be used for many repeated concatenations, like for adding items to a hash inside a loop. While adding together hashes is fast and is constant time (independent of the size of the hashes added), the resulting hash is a bit slower to read than the hashes added together. Thus after tens... of additions the result can be impractically slow to read.